At present the proportion of renewable energy generation, in particular by wind power installations and photovoltaic installations, is increasing considerably. Such renewable energy generators are generally installed where wind and sun are available and are not primarily installed in the vicinity of load centers—as is customary in the case of conventional power plants. Therefore, regeneratively generated electricity often has to be transmitted over large distances. DC electricity grids are often more cost-effective and more efficient for such transmissions. Intensified additional construction of DC electricity grids is giving rise in many places to mixed AC/DC electricity grids, the control of which is becoming increasingly more complex, in particular insofar as a renewably generated power is generally subjected to greater fluctuations than conventionally generated power.
Short-term changes in energy generation or in energy consumption can be compensated for by a so-called primary control power. Furthermore, converters arranged between AC electricity grids and DC electricity grids can perform power shifts between these grids.
A method for optimizing load flows in mixed AC/DC electricity grids is known from the article “Probabilistic security constrained optimal power flow for a mixed HVAC and HVDC grid with stochastic infeed” by R. Wiget et al. at the Power Systems Computation Conference 2014. In this method, however, a respective load flow is optimized only taking into account stochastic load and generation changes.